front end bucking

So i've been having issues with my bike giving a bucking sensation while cruising around town. i've read where if you're in a higher gear at low RPM's it can cause it to bog down. this doesn't seem to be the case i still have the motion whether i'm at low or high RPM's. i thought that it subsided when i rode faster because i don't notice it, but i realized that the vibrations from the bike just overshadowed the bucking motion and that it is there if i focus hard enough on it. It's becoming an aggravation to ride because i feel like i'm riding on the back of a horse with it constantly bucking my arms. Any ideas or help would be greatly appreciated.

As Edwin has said above although I would like to ask is it just an up and down motion or does it feel as though it wants to pull your steering one way or the other?
First thought is tire, I had one throw a belt and it was a bugger. Your fork oil and seals is also a biggy as it will let road imperfections jump right into your hands. But as my son had on his bike the steering head bearings gave an issue with wanting to jump left or right.

I'll check to see if the wheel is out of round. One of my buddies mentioned that the front brake might be catching on the rotor. Thoughts? I'll check out that stuff in that order, Edwins. @Valerie, it just feels like an up/down motion...not side to side. However, going around corners it gets a little sketchy because while i'm leaning the up/down motion throws off my turn a little. I'll check those things and report back with what i find out. Thank you both for your thoughts.